1. Field of the Invention
The present invention relates to an ink jet recording ink used for an ink jet recording apparatus and to an ink jet recording method.
2. Description of the Related Art
In ink jet recording theory, a liquid or molten solid ink is discharged through nozzles, slits, a porous film, and the like for recording on paper, cloth, film, and the like to record images. Various methods for discharging an ink are suggested, such as a so-called charge-control method in which an ink is discharged using an electrostatic attractive force, a so-called drop-on-demand method (pressure-pulse method) in which an ink is discharged using vibration pressure of a piezoelectric element, and a so-called thermal ink jet method in which an ink is discharged using a pressure generated by forming and growing bubbles at a high temperature, and the like. Images having extremely high resolution can be obtained using these methods.
The ink used in these ink jet recording methods include an aqueous dye ink obtained by dissolving various water-soluble dyes in a liquid medium composed of water and a water-soluble organic solvent, an aqueous pigment ink obtained by dispersing various pigments in a liquid medium composed of water and a water-soluble organic solvent, an oil-based dye ink obtained by dissolving an oil-soluble dye in an organic solvent, and the like.
Among these inks, an aqueous ink containing an aqueous dye dissolved is most frequently used as an ink jet recording ink. The first reason thereof is that the main solvent is water and therefore the aqueous ink is safe. Moreover, the second reason is that the color-developing property of a color image is excellent and a printed image of high quality is obtained because a dye is used. Further, the third reason is that the ink has excellent storage stability.
However, in the case of an aqueous ink using an aqueous dye as a coloring agent, water resistance of an printed image is poor.
To improve water resistance of such an aqueous dye, various studies and developments have been made.
For example, Japanese Patent Application Laid-Open (JP-A) Nos. 2-29687 and 2-255876 suggest a method for improving water resistance of an ink by adding a polyamine to the ink. However, in the case of such an ink, the dissolution stability of a dye is easily lowered due to mutual action with a polyamine, and viscosity is easily increased because of the reaction of a polyamine over time. Therefore, clogging easily occurs and discharge stability of an ink easily deteriorates.
Further, Japanese Patent Application Laid-Open (JP-A) Nos. 3-91577, 4-226175, 4-233975, 4-270286, 4-279671, and 6-93196 suggest a method for improving water resistance of an ink by using a dye having a carboxyl group. However, in the case of such an ink, the dissolubility of a dye is lowered because of the vaporization of water and/or an ammonium ion which is a counter ion, and clogging easily occurs and preservability of an ink tends to be lowered. Further, in the case of such an ink, a printed image becomes bronzed, which easily reduces print quality. Further, in the case of thermal ink jet recording, deposition on the surface of a heater referred to as so-called "kogation" is easily formed and a change in the discharge ability of an ink increases over time.
To improve the above-described problems occurring with the increase in water resistance, in Japanese Patent Application Laid-Open (JP-A) No. 4-226175, there are suggested a method in which dyes whose structure is similar to each other are mixed, a method in which a pH buffering agent is added to an ink, and a method in which a phosphate is added. However, in these cases, even though pH can be stably maintained, improvement in clogging is not sufficient, and improvement in kogation which is problematical in thermal ink jet recording is also insufficient.
Also, Japanese Patent Application Laid-Open (JP-A) No. 7-26178 suggests a method in which an alkali metal compound is added to an ink. However, even though such an ink can improve clogging if the storage period is short, when the ink is stored for a long time, the dissolvability of a dye is decreased, and ink storage stability deteriorates. Further, the ink cannot improve kogation which is problematical in thermal ink jet recording.
Further, Japanese Patent Application Laid-Open (JP-A) No. 7-150086 suggests an ink containing a combination of a dye comprising an ammonium ion as a counter ion and an organic amine. However, the organic amine as exemplified tends to corrode a recording head material, jetting frequency response is lowered, a solid image becomes faint and white streaks are generated. Further, the ink cannot improve kogation which is problematical in thermal ink jet recording.
Further, Japanese Patent Application Laid-Open (JP-A) Nos. 7-166116, 7-238264, 7-238247, and 7-268262 suggest an ink containing a combination of an amine compound, a specific dye, urea or a derivative thereof, a substituted automatic compound, and the like. However, primary or second amine compounds as exemplified tend to cause failure of a heater contained in a recording head because such amine compounds have high chemical activity and easily corrode the recording head material, and tertiary amine compounds as exemplified easily decrease the amount of an ink to be discharged, downgrade the jetting frequency response, makes a solid image faint, and generate white streaks because they have a high molecular weight and therefore increase ink viscosity even if the amount of tertiary amine compound added is small and the viscosity increasing ratio when water is evaporated is high. Further, the ink cannot improve kogation which is problematical in thermal ink jet recording.
Further, Japanese Patent Application Laid-Open (JP-A) No. 8-41398 suggests an ink containing a combination of a specific aminoalkylsulfonic acid, glycine, and an alkali metal hydroxide. However, in this case, responsiveness for pulses applied to the recording head, a solid image becomes faint and white streaks are generated. Further, the ink cannot improve kogation which is problematical in thermal ink jet recording.
As a method for improving the above-described kogation, Japanese Patent Application Laid-Open (JP-A) No. 6-220386 suggests controlling the pH of an ink between 6 and 8 using the amine compound represented by general formula (I), below. However, when pH is controlled between 6 and 8 using a dye having a carboxyl group, kogation is not improved sufficiently, a printed image becomes bronzed, clogging easily occurs. ##STR2##
As described above, no ink jet recording ink has been obtained which has superior water resistance and provides the various abilities required of an ink jet recording ink.